<PRE><B>Question 831406</B>
Ignore for the moment that the grade is marked out of 20.  Let us agree on the following assumption:

1.  We assume that there are no more tests to follow, so if the current test is worth 80% of your grade, then the 73% level you currently have is worth 20% of your grade

2.  Then we can write our equation as:
    0.2 times 73 + 0.8 times x = 80;  That is, 14.6 + 0.8x = 80

3.  From the above, x = (80 - 14.6)/0.8 = 81.75

4.  In other words, you must score 81.75% on this test

5.  But the test is marked out of 20, so your score must be 81.75% of 20 = 16.35</PRE>